Autistic Disorder (AD) is a pervasive developmental disorder which is typically diagnosed during childhood. Children with AD often have problematic behaviors which can make them extremely difficult to manage by caretakers, teachers, and therapists. Pharmacologic interventions directed at reducing dysfunctional behaviors in youngsters with AD have primarily included dopamine-blocking antipsychotic agents and serotonergic re-uptake inhibitors. The purpose of this study is to examine whether the atypical antipsychotic agent risperidone may be successful in ameliorating dysfunctional behaviors in children with AD. We hypothesize that because risperidone effects both serotonergic and dopaminergic neural transmission, that this medication will be effective in treating youngsters with AD. All patients who have enrolled in this study have had a significantly positive therapeutic response to risperidone. Due to the small sample size, no results of any statistical analyses are yet available.